Polylactic acid is a bio-derived resin having biodegradability, and its use in the field of containers, such as bottles, is under consideration from the aspect of environment.
By the way, polylactic acid is weak in alkali resistance as compared with polyester such as polyethylene terephthalate (PET), and has low resistance to environmental stress crack (ESCR) due to internal pressure. These drawbacks hamper its commercialization, particularly, in uses for pressure-resistant bottles to be filled with carbonated beverages.
To improve the properties of films or containers made of polylactic acid, proposals have been made for resin compositions having polyolefins, such as polyethylenes, blended with polylactic acid (see Patent Documents 1 to 7). Even bottles formed from these resin compositions are not satisfactory in resistance to environmental stress crack (ESCR) due to internal pressure.